1. Field of the Invention
The present invention relates to a system and method for processing materials and products and, more particularly, is embodied in a closed-cycle, channeled system for processing non-solid products and materials that can be brought to a frozen or solid state by lowering the temperature of the products.
2. Description of the Related Art
Biosolids, or biosludge, is the byproduct of a biological wastewater treatment process and comprises, for example, a mixture of biomass, residual salts and metals, and water.
Costs for landfilling in the United States range from $16 per ton of solids at a waste treatment plant in Oakland to $150 per ton at a landfill in a site in New Jersey. In Europe, disposal costs are more than $500 per ton of residual. Canada and the United States have passed legislation requiring moisture content to be substantially reduced prior to shipping it to regular disposal sites. Several North American landfills require more than 25% solids in waste materials received. Typically, the dewatering, treatment and disposal of biosludges accounts for 30% of capital and 50% of operating costs for utilities. Furthermore, optimized biological treatment systems increased efficiency produce more biosolids that are known to be more difficult to dewater.
Thus, an ever growing concern to governments, industry and environmentalists alike is how biosolids, or biosludge, can be disposed of in a cost effective manner which is not harmful to the environment and which consumes a minimum amount of land fill space. Other biosolids which often need to be dewatered include the byproducts of refineries and oil fields, breweries, industrial waste water treatment plants, ceramics, clay and coal facilities, pulp and paper mills and drinking water filtering plants.
A significant problem of existing dewatering systems is that they are not "closed cycle" systems. In other words, existing sludge dewatering equipment (e.g., belt filter press, filter press, centrifuge, screw press) rely upon various potentially harmful chemical additives. These chemical additives are costly, potentially harmful to the environment and, in some cases, necessitate the collection and treatment potentially harmful, dangerous and/or explosive gases and vapors.
Unlike existing sludge dewatering processes that rely upon polymers to separate water from sludge particles, several embodiments of the present invention advantageously utilize a natural phenomenon called "freeze-thaw" to facilitate a non-chemical liquid/solid separation. Generally, conditioning by freeze-thaw increases the effectiveness of the dewatering process. More specifically, freeze-thaw processes rupture microbial cells and allow entrapped water to escape.
There are different types of water in biosolids produced by an activated sludge system. The four types of water existing within biological system solids are: (1) free (or bulk) water--water not associated with suspended solid particles; (2) interstitial water--water trapped in the crevices and interstitial spaces of the flocs and organisms; (3) viccinal water--multiple layers of water molecules held tightly to the particle surface by hydrogen bonding; and (4) water of hydration--the water chemically bound to the particles. It has been observed that freeze-thaw conditioning is particularly effective at reducing interstitial and viccinal moisture.
The rates at which various product processing steps occur have a direct bearing on the efficiency of the overall process. A significant aspect of the present invention is that certain embodiments include channeled sub-units which effect a more efficient rate of freezing, thawing, etc. In one embodiment of the present invention, the sub-units of the system include a freeze unit, a thaw unit and a low temperature condenser unit which operate together as an integrated system, yet which are also modular and individually useful for processing certain products. For example, the freeze unit, as a stand-alone unit, can be suitably employed as an automated, high-volume block production system for processing juices, fruits and food products including, but not limited to, chicken parts, broth and gravies, meat products, seafood and eggs.
For completeness, reference is made to U.S. Pat. No. 5,029,453, granted Jul. 9, 1991, inventor J. Stirling Scherer, which discloses a channel block system for freezing material.
One object of the present invention is to provide a system and method for closed-cycle processing of non-solid products that can be brought to a solid state by lowering the temperature of the products.
Another object is to provide a closed-cycle system for efficiently dewatering biosolids or other non-food and/or food products without employing potentially harmful chemicals.
Another object is to provide a product processing system with a plurality of interconnected, channeled, modular sub-units which operate together as an integrated system or individually to process certain products.
Another object is to provide a stand-alone freeze unit including a plurality of channels for efficiently and automatically freezing juices, fruits and other non-solid food products into blocks.
Another object is to provide such a freeze unit which additionally includes a mechanism adapted to automatically advance frozen products from the channels and to clean the inside of the channels after the frozen products are removed.
Another object is to provide a product processing system wherein a plurality of plates define product processing channels as well as provide structural support to the system.